Emphysema is defined as an abnormal enlargement of the air spaces distal to the terminal bronchioles with destruction of the alveolar walls. Such air space enlargement is well demonstrated in this slide and a significant diminution in lung parenchyma is obvious.

Note the large open spaces on the right side of the screen and the large round space in the bottom right . These large spaces represent the grossly distended repiratory bronchioles that are characteristic of centrilobular (centriacinar) emphysema. In this type of emphysema, the destruction is in the respiratory bronchiole and the distal alveoli and their ducts are spared. Panacinar emphysema results in the destruction of both respiratory bronchioles and alveoli.